Systemic, multi-stakeholder collaboration to achieve zero-waste cities and decarbonised industrial systems

Abstract: Achieving zero-waste cities and decarbonised industrial systems requires a systemic shift from linear to circular value chains, enabled by multi-stakeholder collaboration. The United Circles project, funded by the EU Horizon Europe programme (Grant 101178798), pioneers new governance models to drive this transition. Coordinated by CARTIF (Spain) with 48 partners, the project promotes urban-industrial symbiosis through mission-driven networks called Hubs4Circularity. United Circles positions a neutral, facilitating Hub4Circularity as essential for coordinating diverse stakeholders—governments, industry, academia, and the waste sector—to ensure equitable participation and decision-making. These hubs manage stakeholder engagement, technology evaluation, investment mobilisation, and implementation oversight, fostering systemic knowledge exchange and network formation. The project targets three key material streams: construction and demolition waste, urban and industrial wastewater, and food waste, supporting 15 innovative circular solutions such as 3D-printed recycled construction materials, wastewater resource recovery, and bioplastics from used cooking oil. These solutions are embedded within regional hubs to scale adoption, attract investment, and enhance resilience. United Circles aims to demonstrate near-zero-waste cities through commercial-scale pilots; reduce resource consumption (e.g., 50% freshwater savings and 90% solid waste recycling at a Spanish wastewater site); foster healthier, low-emission urban environments; and strengthen international cooperation aligned with the European Green Deal. Pilots in Spain, Italy, and Turkey validate these interventions, while “mirror” and “seed” hubs in Hungary, South Africa, Lebanon, and Austria support contextual adaptation and broader uptake of the hub model. This paper presents the conceptual foundation and strategic implementation of the Hubs4Circularity model, highlighting its transformative potential to scale circular practices across diverse socio economic contexts. It underscores the necessity of a neutral, multi-stakeholder governance structure and details the tools, frameworks, and support mechanisms critical for effective hub operation.

Authors: Christina Krenn, Johannes Fresner, Fernando Burgoa Francisco, Dr. Rembrandt Koppelaar